Insulation materials for electrical machines such as generators, motors, and transformers generally include a glass cloth and/or a combination of a glass cloth, a resin binder, a mica tape, and similar materials. Such insulating materials generally need to have the mechanical and the physical properties that can withstand the various electrical rigors of the electrical machines while providing adequate insulation. In addition, the insulation materials should withstand extreme operating temperature variations and provide a long design life.
In recent years, the thermal conductivity of general insulation has improved from about 0.3 W/mK to about 0.5 W/mK (Watts per meter per degrees Kelvin) via the addition of high thermal conductivity fillers. Specifically with respect to stator bars, however, E-glass (electrical fiberglass) generally is used to insulate the conductors, as a vertical separator, and as a backer in insulating tapes. Such E-Glass may have a thermal conductivity of about 0.99 W/mK. Similarly, a Dacron glass (Daglass) also may be used. Daglass may have a thermal conductivity of about 0.4 W/mK.
By reducing the thermal resistance of the stator bar components, improved heat transfer may be obtained between the stator bar conductors and the stator core. Specifically, the current density of the copper conductor may be increased by effectively cooling the conductors. There is thus a desire for even further thermal conductivity improvements so as to produce more power from a smaller unit at a more economical cost or at a higher efficiency from an existing unit.